Yellow Fever, Folklore, Science and Management

In 1793, the city of Philadelphia was terrorized by an epidemic of Yellow Fever. The disease ravaged the city, killing about 5,000 people, approximately 10% of the population. Although the disease had been seen in the Americas as early as the 1600’s, there was little understanding of its pathogenesis nor its treatment. This lack of understanding, along with Yellow Fever’s horrifying symptoms, and often fatal outcome, paralyzed Philadelphia.

At the time, Philadelphia was the center of America, its largest city and national capitol. The Yellow Fever epidemic led to a temporary disbanding of the Federal government. Healthy people fled town, in some cases abandoning ill relatives. Those left behind did their best to avoid contact with others. Commerce and other public activities came to a grinding halt. The poor and homeless were left to die in the streets with hospitals too scared to admit them.

A prominent physician, Benjamin Rush, believed he had found a cure. Rush was a leading citizen who had been a signer of the Declaration of Independence. Reading through some old published letters, he found a reference to a previous outbreak of Yellow Fever that had taken place in Virginia. The letter indicated that the disease caused the stomach and intestines to be filled with blood, that needed to be purged.

Bloodletting was still a commonly accepted medical practice in the 1700’s. Rush started to aggressively administer bloodletting to patients inflicted with the disease. He made claims that many of his patients recovered after his treatment. When a patient died after treatment, Rush would explain that their illness was too severe and would have been unresponsive to any treatment. While he was criticized by many of his peers in the medical community, they practiced their own ineffective folk remedies.

The epidemic was temporarily halted only by the emergence of the winter, and colder weather. However, it remained an ongoing problem for Philadelphia, with smaller outbreaks in the late 1790’s. In 1802, Yellow Fever claimed the lives of 29,000 French troops sent by Napolean I to support France’s claim to New Orleans. It continued as a major source of illness throughout the 1800’s.

While Yellow Fever continued to claim tens of thousands of lives in the 19th century, several physicians were making progress in understanding its causes. A Cuban doctor and epidemiologist, Carlos Finlay, believed he had identified the method by which the disease was transmitted. The previous theories were that the disease spread from unsanitary conditions in a city (e.g. open sewage) or from direct contact with an infected individual, his clothes or his bedding. Instead Finlay hypothesized correctly that the disease was spread by a particular species of mosquito. However, due to his lack of understanding of incubation periods, he was unable to demonstrate his theory experimentally with human subjects. He presented his findings to an international conference in Washington in 1881. Unfortunately, the scientific community rejected his theory and no further progress was made in eradicating Yellow Fever.

In the 1890’s, during the Spanish-American war, tens of thousands of servicemen from both sides contracted the disease. In fact, more soldiers were killed by the disease than by enemy forces. The disease didn’t acknowledge rank, decimating a large number of senior officers. At the end of the war the U.S. government realized that Yellow Fever posed a major threat to the occupying forces abroad in Cuba. They established a Yellow Fever Commission headed by an Army surgeon, Walter Reed.

Reed and his team arrived in Cuba and set about trying to find the cause of transmission. He was convinced that Yellow Fever wasn’t directly contagious as caretakers rarely acquired the disease. He reviewed a paper written by a Dr. H. R. Carter who showed that the incubation period for the disease (i.e. time between exposure and symptoms) was five days. However, other people in the patient’s household were not infected for fifteen to twenty days. This led Reed to hypothesize that some intermediate agent had an incubation period of ten to fifteen days. Building on the findings of Finlay, he conjectured that the mosquito was that intermediate agent.

Reed and his team set up a series of clever and effective experiments to attempt to confirm the mosquito hypothesis. They constructed a special camp just outside of Havana. They built a team of subjects from paid military volunteers. In one study, a mosquito was placed in a test tube which was applied to the skin of an infected Yellow Fever patient. The mosquito would bite the individual, drawing a quantity of their blood. After varying waiting times (to test incubation periods), the test tube was placed on the arm of a healthy subject. The mosquito then bit the healthy individual. Sure enough, if the incubation period was sufficient, the volunteers became infected with Yellow Fever. In another experiment, the volunteers slept with the dirty clothing and bedding of infected individuals. Despite 20 nights of exposure, no subjects became infected. In a 3rd experiment, the building was partitioned by mosquito-proof wiring. On one side, subjects lived with liberated, infected mosquitoes. On the other side, subjects lived in a mosquito free area. Many of the subjects exposed to the mosquitoes became ill. None of the subjects in the mosquito free area came down with the illness. This demonstrated that no underlying element in the building was the causal factor.

These series of experiments allowed Reed to conclude that the mosquito was the sole transmission vector. Now that the cause was understood, an action plan could be established to eradicate the disease. Another phyiscian, Dr. William Gorgas was given the task of eliminating the mosquitoes that were now known to cause the disease. He and his men destroyed mosquito breeding grounds in Cuba by spraying them with oil to kill the hatching larvae. The effect was miraculous, with no new reported cases of Yellow Fever. Mosquito population control became a standard and effective practice in areas prone to Yellow Fever. It took another 35 years for the South African virologist to develop a vaccine for Yellow Fever. He was awarded a Nobel Prize in 1951 for this accomplishment.

We could end our story of Yellow Fever at this point, an inspiring epic of suffering, sacrifice, persistence and grand accomplishment. But there is a profound theme weaving its way through this tale. This story chronicles the historical maturity of the practice of medicine as well as the dangers of unscientific thinking. Although Francis Bacon had first promoted the idea of the scientific method in 1620, medicine in the time of Benjamin Rush was still practiced in a decidedly informal manner. Most medical procedures were based on folklore; customary practices that had been handed down through the generations. Many of the ideas regarding causes of illnesses or effective cures reflected superstitious, supernatural or theological explanations. One prevalent theory, dating back to Ancient Greece, posited that all illness resulted from an imbalance of four Humors within the body. This theory led to practices like bloodletting as a means to “rebalance” the humors.

In examining Rush’s perspective and practices, one can see the pernicious impact of cognitive biases and non-scientific thinking. For starters, Rush was a victim of confirmation bias. This is the human tendency to seek confirming evidence for one’s beliefs and to reject or ignore disconfirming evidence. Rush took immediate credit for patients that appeared to get better after his treatment. He simply dismissed as hopeless cases, those patients that died after his care. In doing so, he also violated a basic idea of scientific research known as falsifiability. This concept, initially described by the philosopher Karl Popper, states that a theory can not be useful if an experiment couldn’t hypothetically disprove it. In Rush’s treatment of Yellow Fever victims he adopted a “heads I win, tails you lose” philosophy. That is, no evidence would convince him that his theory was wrong and needed to be revised.

The idea of bloodletting itself, is an example of the cognitive bias known as representativeness. This is the human tendency to intuitively look for “likeness” when exploring causality. That is, the notion of purging fluids from the body intuitively makes sense as a way to “eliminate” an illness inside us. A more obvious example of representativeness is seen in a number of pseudoscientific supplements. For example, supplements derived from owls are thought to improve vision (due to the superior eyesight of these birds).

In contrast to Rush, Walter Reed utilized scientific methods to isolate mosquito bites as the sole cause of the spread of the disease. His studies had many of the elements that we recognize today as part of sound experimental design. He was testing for a specific outcome. His experiments were designed with control groups (individuals not exposed to the illness) to demonstrate the validity of his theory. He also tested multiple ideas (i.e. exposure to contaminated items) to eliminate alternative causes. In addition to his strong experimental design, Reed also utilized the helpful practice of leveraging past research. He incorporated the scientific ideas of Finlay and Carter as starting points for own theories.

In hindsight, it’s easy to look backwards and question the wisdom, practices and insights of doctors from the past. With all we know now about disease and scientific practices, it seems preposterous that learned men could practice their craft in such an ignorant and barbaric manner. But certainly these doctors weren’t practicing their profession in an intentionally harmful manner. By and large, they were educated, intelligent and caring professionals. Unfortunately, they lived at a time when folk medicine dominated their field. The scientific practices that we take for granted today had not yet taken hold.

Lest we get too cocky about our own professionalism, consider the following questions. How will historians in 2050 look back at the practice of management in large enterprises in the early 2000’s? Is it possible that the average knowledge worker in an enterprise pursues their craft with the same lack of scientific rigor as Rush did in 1793? I believe that a reasonable comparison can be made. Confirmation bias, representativeness bias, unverifiable theories and unscientific practices abound within the modern corporate enterprise.

Ask yourself the following questions:

Does your organization have a number of historical practices in place with no evidence of their effectiveness?

Are many of these practices simply the result of folklore or intuition, as opposed to being evidence tested?

When introducing a new or changed process, do you have the ability to measure its impact?

When making decisions, do the results meet the test of falsifiability? Would you be able to determine if positive results were caused by hidden factors as opposed to your actions?

Does your organization have a culture of openness to new ideas and alternative thought processes? Or are people inclined to violently defend their pet ideas?

Much can be learned by exploring the history of the practice of medicine. While hardly perfect, the medical field has established a strong culture of utilizing scientific practices to inform research, diagnosis and treatments. The professional practices of the typical corporate knowledge worker lacks the scientific rigor seen in such fields as medicine. Forward thinking organizations would be wise to incorporate more scientific process to their research, decision making and effectiveness measurement. Failing to do so may leave your performance improvement practices in the same league as bloodletting.